C Preprocessor Remove Trailing Comma

I have a macro like this:

#define C( a... ) ( char *[] ){ a, 0 }

This works for non-empty arguments:

C( "a", "b" ) => ( char *[] )( "a", "b", 0 }

But I want to remove the trailing comma when provided with an empty argument:

C() => ( char *[] ){ , 0 }

Is this possible?